The brushes, or carbon brushes, of an electric motor are generally supported by a support plate having a central passage which allows the rotatable commutator, secured on the shaft of the motor, to be introduced into a position in which it lies in line with the brushes. When the motor is assembled, the brushes are guided and resiliently biassed towards the passage formed in the support plate, so that they then engage frictionally against the commutator and thus allow the current to be conveyed from the input terminals to the rotor of the motor via the commutator.
Some known arrangements are so constructed that they have brushes which, when they are not mounted on the motor, are naturally urged towards the central passage of the support under the resilient action of a spring. In addition, it is necessary to assemble this device manually, and this calls for the use of mechanical means such as a screwdriver for example, to push the brushes back in their respective guides in order to enable the commutator to be introduced into the central passage of the support plate. Such arrangements are not well suited for assembly methods using robotic assembly lines.
In addition, it has also been proposed, for example as described in U.S. Pat. No. 4,866,322, to provide such devices with stop means for retaining the brushes in a position spaced away from the central passage of the support plate so as to allow the commutator to be introduced. The brushes are released after the commutator has been fitted in position, so that they can then come into contact with the latter. To this end, a brush is held by means of a resilient lever, which is connected to the brush holder support plate and which has a protuberance which cooperates with a recess formed in the brush, maintaining it in its guide out of the central passage of the support plate. The motor casing accordingly has an appropriate cut-out portion which allows it, during its assembly and after the commutator has been introduced into the passage, to cooperate with the lever with a view to disengaging the protuberance from the recess in the brush and thus releasing the latter.
However, such a device has certain drawbacks. In practice it is desirable to provide a motor casing, a brush carrier support plate and a lever which are specially designed. This increases production costs. In addition, this cooperation of the lever and the motor casing must be arranged so that it will not take place in a faulty manner, particularly as a result of manufacturing tolerances, which can give rise to hindrance in the releasing of the brushes.
The invention aims to provide a solution for this problem.